import java.util.Arrays;
import java.util.Scanner;

class Main1 {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String str = scanner.nextLine();
        String ret = "";
        int i = 0;
        while (i < str.length()) {
            int j = i;
            while (j < str.length() && str.charAt(j) >= '0' && str.charAt(j) <= '9') {
                j++;
            }
            if(j-i > ret.length()) {
                ret = str.substring(i,j);
            }
            i = j+1;
        }
        System.out.println(ret);
    }
}


public class Main {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     *
     * @param numbers int整型一维数组
     * @return int整型
     */
    public int MoreThanHalfNum_Solution (int[] numbers) {
        // write code here
        Arrays.sort(numbers);
        return numbers[numbers.length/2];
    }
}
